1. Field of the Invention
This invention relates to hydraulic tools, and more particularly to hydraulic tools that can use a constant pressure fluid delivery system or a constant volume fluid delivery system. In particular, this invention relates to a hydraulic tool having a selector sleeve that is selectively adjustable to operate the tool in an xe2x80x9copen centerxe2x80x9d (OC) mode or a xe2x80x9cclosed centerxe2x80x9d (CC) mode.
2. Description of Related Art
U.S. Pat. No. 5,778,755 is directed to a control apparatus 22 for operating a hydraulic tool 20 that can use a constant volume or constant pressure fluid system. The constant volume or OC mode of operation is shown in FIGS. 1-3, and the constant pressure or CC mode of operation is shown in FIGS. 4 and 5.
The control apparatus 22 includes a housing 32 having a cavity 34 in which a piston 36 reciprocates. The piston 36 divides the cavity 34 into a drive chamber 44, which is positioned to the left of the piston 36, and a retract chamber 42, which is positioned to the right of the piston 36. An adjustment assembly 48 is retained in the drive chamber 44 to control fluid flow between the retract chamber 42 and the drive chamber 44 in a neutral mode. The control apparatus 22 also includes a handle structure 49 containing a valve assembly 50. Inlet and outlet ports 52, 54 can be connected to a constant volume or constant pressure fluid source. A central port 56 selectively connects the inlet port 52 with the retract chamber 42. A cross port 58 communicates with the drive chamber 44 and selectively with the outlet port 54.
The piston 36 includes a plurality of shuttle valves 66 having shuttle spools 68 that are retained in shuttle ports 70 formed in the piston 36. Enlarged heads 72, 74 are provided on each end of the shuttle spool 68. Each shuttle valve 66 operates along a valve axis 78 that is generally parallel to the central axis 76.
The adjustment assembly 48 allows the control apparatus to be operated in the OC or CC mode. The adjustment assembly 48 includes a control body or annular member 82 which is attached to adjustment shafts 84 extending through a shaft bore 86 in the housing 32. The control body 82 can be moved between a first position (FIGS. 1-3) and a second position (FIGS. 4 and 5) by use of drive heads 96 that are connected to the adjustment shafts 84, and are accessible to the outside of the housing 32. In the first position, the control body 82 extends away from a recess 106, and in the second position, the control body 82 is received within the recess 106. The control body 82 has an annular shape that provides a continuous circumferential contact surface 102 that can contact the shuttle valves 66 (FIG. 1) regardless of their circumferential orientation.
When the adjustment assembly 48 is configured for use with a constant volume system, the shuttle valves 66 are moved as a result of contacting the adjustment assembly 48 when the piston 36 is retracted. Movement of the spool valves 66 unseats valve heads 74 from the shuttle port 70. By disengaging the heads 74 fluid flows from the retract chamber 42 to the drive chamber 44 when the piston is in a neutral position as shown in FIG. 1. As shown in FIG. 4, the adjustment assembly is spaced away from the spool valves 66 for use with a constant pressure system thereby preventing engagement with the shuttle spool valve 66 causing the spool valve heads 74 to seal the shuttle port 70 when the piston 36 is in a neutral position.
A step-by-step description of the operation is now described. In FIG. 1, the adjustment assembly 48 is positioned in the constant volume or OC mode. The piston 36 is in the fully retracted position in which the shuttle valves 66 are opened by contact of the head 72 against the control body 82. This neutral position allows fluid to continuously flow from the inlet port 52, through the control apparatus 22 (i.e., the central port 56, tubular conduit 108, retract chamber 42, and around valve spools 66), and back through the outlet port 54 via cross port 58.
In FIG. 2, trigger 64 is actuated to communicate the inlet port 52 with the cross port 58, which in turn supplies pressurized fluid to the drive chamber 44 to drive the piston 36. During this movement, the heads 72 are maintained in their position against the piston. Fluid from the retract chamber 42 is exhausted through the central conduit 108, the central port 56 and the outlet port 54.
In FIG. 3, the trigger 64 has been released following a crimping operation. Release of the trigger 64 re-establishes communication between the inlet port 52 and the central port, central conduit 108 and the retract chamber 42 to slide the piston 36 to its retracted position. During this movement, the spool valves 66 slide on the piston 36 so that the heads 74 contact the piston 36, until such time as the piston reaches the fully retracted position. At that time, the heads 72 engage the control body 82, and the heads 74 are separated from the piston 36 to allow pressurized fluid to pass though the piston 36 and to the outlet port 54 via the cross port 58.
The closed volume or CC mode of operation is shown in FIGS. 4 and 5. The only difference in these figures is that the control body 82 has been placed in the recess 106 so that it does not contact the heads 74 when the tool is in the neutral position, (FIG. 4). As such, the pressurized fluid (that is supplied via the inlet port 52, central conduit 56 and tubular conduit 108) is maintained in the retract chamber 42 and does not pass through the piston 36.
The operation of the tool in the CC mode in FIG. 5 is the same as the operation of the tool in the OC mode in FIG. 2. Further, when the trigger is released, the shuttle valves 66 will slide such that heads 74 contact the piston 36. However, upon reaching the fully retracted position, the heads 72 will not contact the control body 82 so that constant pressure is maintained on the piston 36.
U.S. Pat. No. 5,442,992 patent discloses a reciprocating hydraulic tool 20 in the form of a shade tree pruner. The tool 20 includes a cylinder 40 having a piston 34 that reciprocates between a fully extended position and a retracted position. The tool 20 is referred to in the art as a xe2x80x9cpull to cutxe2x80x9d tool since the blades 26, 28 of the pruner start in the open position, and when the trigger 90 is actuated, hydraulic fluid is supplied to the side of the piston 34 remote from the trigger 90. This causes the piston to move toward the trigger, and the blade 26 is pulled toward the blade 28 to perform a cutting operation.
The tool 20 can use either a constant pressure (CC) or a constant volume (OC) source of hydraulic fluid. A selector 60 is rotatably mounted on the cylinder to enable the tool to be used in the OC or CC modes. FIGS. 1 and 2 show the selector 60 in the OC mode, and FIGS. 3 and 4 show the selector in the CC mode.
In FIGS. 1 and 2, the selector 60 defines a passageway 62 that communicates between opposite sides of the piston 34 when the piston is in its fully advanced position with respect to the cylinder, as shown in FIG. 1. In this fully advanced position, the piston is fully advanced with respect to the end 58 of the cylinder which is opposite its end 44 at which the valve body 42 is coupled.
In the second position of the selector 60 as illustrated in FIGS. 3 and 4, the passage 62 is rotated out of a position for communicating between the opposite sides of the piston 34. Additionally, the passage 62 mounts a one-way check valve 68 that limits fluid flow to a single direction, from a side 70 of the piston 34 that faces the first end 44 of the cylinder and the opposite side 56 of the piston that faces the opposite end 58 of the cylinder 40.
In FIGS. 1 and 3, the tool 20 is in the neutral position. Hydraulic fluid is supplied by the pressure port 49 to a cross port 52 that supplies the fluid to the cylinder 40, which is maintained in the fully extended position. Fluid from the opposite side of the piston is exhausted through the conduit 54, short port 55 and outlet port 51.
In FIG. 1, the selector 60 is positioned such that, when the piston is in the fully extended position, the fluid can enter the passageway 62 of the selector 60, pass through holes 64 and 66 in the cylinder 40, the check valve 68, and return to the conduit 54 and outlet port 51. This is the OC mode of operation.
FIG. 3 differs in this respect because the selector 60 is rotated so that the passageway 62 does not align with the holes 64, 66 of the cylinder 40, which disables communication between the opposite ends of the piston 34. Therefore, fluid is supplied to the cross port 52 and the left side of the piston, while fluid from the right side of the piston is exhausted. This is the CC mode of operation.
In FIGS. 2 and 4, the trigger has been actuated to perform a cutting operation. Fluid is supplied to the conduit 54, which in turn provides the fluid to the side 56 of the piston 34 that is remote from the trigger. At the same time, fluid is exhausted (via cross port 52, axial port 92, and outlet port 50) from the side 70 of the piston that faces the trigger. This causes the piston to move toward the trigger.
As opposed to FIGS. 2 and 4 (the CC mode), the selector 60 in FIGS. 1 and 3 (the OC mode) is positioned so that fluid can flow from the holes 64, 66 into the passageway 62. However, the ball 80 of the check valve 68 is maintained in the closed position by use of a spring 82.
The 755 and 992 patents are complicated in design and require that a short circuit for the OC mode of operation be provided by using a passage in or around the piston. Thus, a need has developed in the art to provide a hydraulic tool in which modification of the piston and/or the cylindrical housing is not necessary to short circuit flow in the OC mode of operation.
One aspect of the invention is to provide a hydraulic tool having a selector member that can be switched easily between the OC and CC modes of operation. The tool may be a reciprocating tool such as a crimper, but it is not limited to reciprocating type tools.
Another aspect of the invention is to provide a hydraulic tool, which is preferably piston actuated, in which a short circuiting hole or conduit can be provided in an oil tube that communicates between the valve spool and a side of the piston opposite the oil tube. The short circuiting hole or conduit can be provided such that fluid need not go around, through or even reach the piston and/or a cylinder that houses the piston.
According to one exemplary embodiment of the invention, a hydraulic tool switchable between an open center mode and a closed center mode and having a work mode and a neutral mode comprises a cylinder defining a chamber, a piston within the chamber and operable in the neutral mode and the work mode, the piston defining a drive chamber and a retract chamber within the chamber, a valve operable to selectively supply hydraulic fluid to the drive chamber to thereby drive the piston to a first position when the tool is in the work mode, and to selectively supply the hydraulic fluid to the retract chamber to thereby move the piston to a second position when the tool is in the neutral mode, a fluid inlet and a fluid outlet in fluid communication with the valve; an oil tube in fluid communication with the valve and extending through the piston and being in communication with the retract chamber, the oil tube including opposite ends and at least one hole between said ends, and a mode selector being positionable between a first position in which the tool can operate in the open center mode in which the tool can utilize a constant volume fluid delivery source, and a second position in which the tool can operate in the closed center mode in which the tool can utilize a constant pressure fluid delivery source. In the open center work mode the valve is configured to supply the hydraulic fluid through the oil tube to the drive chamber to drive the piston to the first position. When the tool is moved to the neutral mode, the valve is configured to supply the hydraulic fluid through the oil tube to the retract chamber such that movement of the piston to the second piston can allow communication between the inlet and outlet through the at least one hole in the oil tube.
According to another exemplary embodiment of the invention, a hydraulic tool comprises a cylinder defining a chamber and a piston within the chamber and operable in a neutral mode and a work mode, the piston defining a drive chamber and a retract chamber within the chamber. A valve is operable to selectively supply hydraulic fluid to the drive chamber to thereby drive the piston when the tool is in the work mode, and to selectively supply the hydraulic fluid to the retract chamber when the tool is in the neutral mode. A mode selector member is positionable between a first position in which the tool can operate in an open center mode in which the tool can utilize a constant volume fluid delivery source, and a second position in which the tool can operate in a closed center mode in which the tool can utilize a constant pressure fluid delivery source. In the open center mode when the tool is in the neutral mode, the valve is configured to supply the hydraulic fluid to the retract chamber until filled, whereupon any excess hydraulic fluid is exhausted to an outlet port before it reaches the chamber or the piston.
In yet another exemplary embodiment of the invention, a hydraulic tool comprises a cylinder defining a chamber, a piston within the chamber and operable in a neutral mode and a work mode, the piston defining a drive chamber and a retract chamber within the chamber, and a valve operable to selectively supply hydraulic fluid to the drive chamber to thereby drive the piston when the tool is in the work mode, and to selectively supply the hydraulic fluid to the retract chamber when the tool is in the neutral mode. The tool can operate in a open center mode in which the tool can utilize a constant volume fluid delivery source. In the open center mode when the tool is in the neutral mode, the spool is configured to supply the hydraulic fluid to the retract chamber until filled, whereupon any excess hydraulic fluid is exhausted to the outlet port before it reaches the chamber or the piston.
These and other aspects of the invention will be described in or become apparent from the following detailed description of preferred embodiments.